s a **lubricant**: it forms a layer between the touching teeth and reduces this friction. This identifies the required physical effect for **B1**.","highlights":[{"text":"Grease is applied to the interlocking metal gears","location":"specification"}]},{"type":"text","order":1,"title":"Track the wasted energy","content":"With less friction, the gears do less work against friction. Therefore, less energy is dissipated as wasted **thermal energy** (heating) to the gears and their surroundings.\n\nThis cause-and-effect explanation earns **M1**."},{"type":"hyper_latex","block":{"nodes":[{"latex":"E_{\\mathrm{input}}=E_{\\mathrm{useful\\ kinetic}}+E_{\\mathrm{wasted\\ thermal}}"},{"latex":"\\htmlData{anchor=wasted-down}{E_{\\mathrm{wasted\\ thermal}}\\downarrow}\\quad\\Rightarrow\\quad\\htmlData{anchor=useful-up}{E_{\\mathrm{useful\\ kinetic}}\\uparrow}"},{"latex":"\\mathrm{efficiency}=\\frac{\\htmlData{anchor=useful-ratio}{E_{\\mathrm{useful\\ kinetic}}}}{E_{\\mathrm{input}}}"}],"highlights":[{"color":"green","anchor":"useful-up"}],"connections":[{"to":"useful-ratio","from":"useful-up","color":"green","label":"larger useful output"}]},"order":2,"title":"Link it to efficiency","description":"For the same input energy, reducing the wasted thermal energy means a greater proportion is transferred as useful kinetic energy to move the belt. A1: This greater useful kinetic-energy proportion means the conveyor belt system's efficiency increases."}]}],"generatedAt":"2026-07-22T12:03:28.351Z","modelVersion":"gpt-5.6-terra+diagrams-1","explanationVersion":"v3"},"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"1213915a-6ec0-4e3c-a068-e324639a3c9d","revisionId":"de00f8e2-5fec-4e80-8fcd-fa477532d32c","questionNumber":null,"questionType":"LA","specification":"In an island territory, electricity is generated using both fossil fuels (non-renewable) and renewable energy resources.\n\nThe graph in Figure 1 shows the annual amount of electricity generated by these two types of resources from 2012 to 2024.\n\n![Graph of electricity generation trends in an island territory from 2012 to 2024](https://assets.mathsgenie.co.uk/aqa-qb/fc64457b-d2a9-4e11-9fe5-70a4f1a7baca.png)","difficulty":4,"difficultyBand":"medium","totalMarks":6,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"d60d87d1-fc78-4604-b5d3-bd07af3c7b06","label":null,"content":"Explain how and why the amount of electricity generated by fossil fuels and renewable energy resources changed from 2012 to 2024.\n\nYour answer should include:\n- a description of the trends shown in Figure 1, using data from the graph\n- reasons for the decrease in fossil fuel use\n- reasons for the increase in renewable energy use","markscheme":"- Identifies the trend for fossil fuels, showing a decrease from $45\\text{ PJ}$ in 2012 to $15\\text{ PJ}$ in 2024 A1\n- Identifies the trend for renewable resources, showing an increase from $10\\text{ PJ}$ in 2012 to $35\\text{ PJ}$ in 2024 A1\n- Pinpoints the crossover year of 2020 where renewable generation overtook fossil fuels at $25\\text{ PJ}$ A1\n- Explains the decline in fossil fuel use due to environmental impacts (e.g., release of greenhouse gases like $\\text{CO}_2$ causing global warming, sulfur dioxide causing acid rain) or their finite nature M1\n- Explains the rise in renewable energy use due to sustainability (they do not run out), zero $\\text{CO}_2$ emissions during operation, or advancements in efficiency and cost-effectiveness of wind/solar technologies M1\n- Presents a well-structured, coherent argument that clearly links the graphical trends with logical environmental and technological explanations C1","marks":6,"order":0,"markingRubric":null,"explanation":{"methods":[{"id":"structured_explanation","label":"Build a linked explanation","steps":[{"type":"text","order":1,"title":"State the fossil trend","content":"Start with a direct comparison of the endpoints:\n\n> Fossil-fuel electricity generation **decreased** from

Efficiency and energy resources

Question 2

Efficiency and energy resources Questions

Efficiency and energy resources

Question 2

Efficiency and energy resources Questions